I noticed that turning them 4 + times a day works better than turning them less. I also candle mine a whole lot because I like watching them develop. I don't see the harm in candling. I always wash my hands before I do it, and the candler bulb is warm so it is not like the egg will chill a lot. Peahens get off the eggs for a bit to eat and drink, so it is just like what a peahen does.
My book that came with the incubator said to and the last 3 days do not open it up until all that are going to have hatched.
My styrofoam incubator manual says that too.
There's a study that showed the ideal number of times to turn chicken eggs is 96 per day. Many other websites say to set the bator to turn once an hour. Not saying anyone do anything differerent, just wanted to share.
-Kathy